Canadian singer Justin Bieber performs at the O2 Arena in east London Friday night. / Joel Ryan, Invision/AP

by Kim Hjelmgaard, USA TODAY

by Kim Hjelmgaard, USA TODAY

LONDON - Justin Bieber's "rough week" came to a mostly smooth end on Friday night in London, where the Canadian singer was playing his fourth concert in a week at the O2 arena.

He may have kept his fans waiting for hours on Monday, suffered breathing problems that required a stay in the hospital on Thursday, and angrily lunged at a photographer on Friday morning, but devotion knows no bounds, especially if you worship at the altar of Justin Bieber - if you are, as the saying goes, a Belieber.

And so when the heartthrob and pop sensation took to the stage of the huge entertainment complex that sits on the Greenwich peninsula in south London - he was late again Friday, but not that late - he played to an audience that seemed more than ready and willing to forgive the recent transgressions.

"We still love him, how couldn't you?" said Rosa Houston, 12, ahead of Friday's show. "He's just having fun. As long as he's on form tonight I'll forgive him," she said. Shelley Houston, Rosa's mother, added, "He's just young, that's all. We love our Bieber."

They certainly do. Many of the fans that had gathered for Friday's performance in London expressed an entirely undiminished enthusiasm for the music star notwithstanding his recent travails in the United Kingdom.

"I hope he's OK given that he fainted yesterday," said Beatriz Rodeia, 16. "I think it was just the stress because he was late for the concert here earlier in the week. He probably just panicked from all the stress and fainted because of that," she said. Rodeia said she thought that episode was probably a reflection of "how much he has going on."

On Monday, Bieber's "Believe" tour will travel to Portugal before fanning further out across Europe, the Middle East, South Africa and North America. He will be on the road until August.

However, the 19-year-old's difficult week was capped Friday by an incident earlier in the day when the music star had an awkward altercation with a photographer outside his London hotel. Bieber was quickly ushered into a waiting van by his security detail only to emerge moments later from the vehicle, shouting, "What did you say? What did you say?"

He later tweeted to his nearly 36 million followers on Twitter, "Ahhhhh! Rough morning. Trying to feel better for this show tonight but let the paps get the best of me." He then added, "Only way someone can break u is if u let them."

The outburst with a member of the press followed a dramatic and whirlwind few days in London for Bieber. On Thursday, he was forced to receive medical treatment after suffering breathing problems while on stage. He took a break then finished the show but subsequently received treatment at the London Clinic.

He later released a picture of himself via Instagram sitting atop what appeared to be a hospital bed. The image was captioned, "gettin better."

Before that, on Monday, Bieber faced the ire of fans when he showed up several hours late for his performance. Many concert-goers, particularly those who had to leave early in order to be able to get home on public transportation, reacted badly.

Still, when Bieber descended onto the O2 arena's central platform on Friday night, there was little to suggest the singer's tumultuous last few days. The dance routines looked reasonably sharp. There were lots of clothes being changed. First white pants, then black. The blazers were on, then off. As were the vests. There was no fainting, no breathing difficulties or scuffling. He looked in control.

"His show is better than anyone's," said Ashley Tonani, 16. "It's better than Coldplay's, it's up there with Michael Jackson," she said. Tonani attended Tuesday's show and was hanging around outside the O2 arena on Friday evening hoping to secure a ticket. (She did not get one.) Tonani said that Bieber's troubles in London this week did not make her think less of the hit maker. "It makes me like him even more," she said. "He's just amazing and gives so much back."

On Friday, part of what he was giving back was the ability to inspire his youthful fan base. "I never in a million years thought that I would have this many fans and perform on this amazing stage," Bieber told the approximately 15,000-strong crowd at one point during his set to huge, deafening applause. "I want to say that you can do the same thing. If you set your mind to something, nothing can hold you back."

However, for Rhian Richards-Levy, 13, there was something to hold back. "I'm not going to lie, there are some things I've heard about him that I don't like (she mentioned drug-taking) and that has made me question him. But it's not like he's the only person in the world who has behaved like this," she said, referring to the tardiness earlier in the week. "It's not that easy to get up there and perform like he does."

There was no stopping Bieber, though. "I want to know who in the audience has been with me from the beginning, when I first started out?" Bieber said toward the end of Friday's performance. All of them, Justin.